Field
The present specification generally relates to combustion systems and, more particularly, to oxycombustion systems and methods in which oxycombustion is conducted together with a thermally integrated ammonia synthesis.
Technical Background
In a carbon-constrained world, energy efficiency and CO2 capture play major roles in controlling CO2 emissions for a sustainable future. The growing worldwide demand for energy is constantly in strife with pushes for protection of the environment. This combination of issues requires ongoing development of systems that are not only energy efficient but also reduce emissions of CO2 and pollutants. Energy efficient systems are most often the fruit of systems integration and energy fluxes management.
Oxycombustion with CO2 capture is a technique to combust fuels with pure oxygen while capturing CO2 and avoiding numerous pollutants. Oxycombustion uses substantially pure oxygen to combust a fuel, leaving the flue gases substantially nitrogen-free, with primarily CO2 and water as waste products or flue gases. It is then possible to cool the flue gases to condense the water and recover the CO2 stream with minimum energy penalty. Typical combustion processes in the presence of nitrogen molecules and oxygen molecules generate nitrogen oxides (NOx), the harmful pollutants that have led to emissions legislation around the world.
Most fossil fuels also contain sulfur compounds that lead to the formation of sulfur oxide (SOx) pollutants when these fuels are combusted or oxidized. In refinery streams, hydrogen produced in the refineries can be used to hydro-treat liquid fuels, for example, and reduce sulfur content. Several processes also exist for post-combustion SOx removal. For example, ammonia injection into a flue gas stream has been found to reduce both NOx and SOx emissions. Nevertheless, in such post-combustion processes the ammonia must be purchased or derived from a separate source at a both an energy cost and a monetary cost.
Ongoing needs exist for fuel combustion systems that operate with increased energy efficiency and that produce fewer harmful emissions of greenhouse gases such as CO2 and pollutants such as NOx, and/or SOx.